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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="geometry.aboutdoc"></a><a class="link" href="aboutdoc.html" title="About this Documentation">About this Documentation</a>
</h2></div></div></div>
<p>
      Within the Boost community there are several styles of documenting. Most libraries
      nowadays are using QuickBook, the WikiWiki style documentation.
    </p>
<p>
      Boost.Geometry started with Doxygen, and during review it was decided to go
      to QuickBook. However, it was convenient to keep Doxygen also there: it does
      a good job of connecting descriptions to function and class declarations.
    </p>
<p>
      Doxygen is able to generate XML (besides the normal HTML output), containing
      all documentation.
    </p>
<p>
      So the challenge was to translate the XML generated by doxygen to QuickBook.
      At least, translate parts of it. Boost contains currently two tools using XSLT
      to go from Doxygen-XML to BoostBook, or to QuickBook. These tools are used
      within Boost.Random and Boost.Asio (and maybe more). However, this XSLT process
      was quite hard, did not deliver (yet) the wished results, and we are all C++
      programmers. So another tool was born, this time in C++ using RapidXML, going
      from Doxygen-XML to QuickBook with the ability to mix both.
    </p>
<h4>
<a name="geometry.aboutdoc.h0"></a>
      <span class="phrase"><a name="geometry.aboutdoc.the_chain"></a></span><a class="link" href="aboutdoc.html#geometry.aboutdoc.the_chain">The
      chain</a>
    </h4>
<p>
      The process is as following:
    </p>
<div class="orderedlist"><ol class="orderedlist" type="1">
<li class="listitem">
          call doxygen to go from C++ to XML
        </li>
<li class="listitem">
          call <span class="emphasis"><em>doxygen_xml2qbk</em></span> to go from XML to QuickBook
        </li>
<li class="listitem">
          call bjam to from QuickBook to HTML
          <div class="orderedlist"><ol class="orderedlist" type="a">
<li class="listitem">
                bjam translates QuickBook to BoostBook
              </li>
<li class="listitem">
                bjam then translates from BoostBook to DocBook
              </li>
<li class="listitem">
                bjam then translates from DocBook to HTML
              </li>
</ol></div>
        </li>
</ol></div>
<p>
      This chain is currently called by "make_qbk.py", a Python script
      which calls the chain above in the right order. Python ensures that the chain
      can be handled in both Windows and Linux environments (it is probably possible
      to call all parts with bjam too).
    </p>
<h4>
<a name="geometry.aboutdoc.h1"></a>
      <span class="phrase"><a name="geometry.aboutdoc.the_reference_matrix"></a></span><a class="link" href="aboutdoc.html#geometry.aboutdoc.the_reference_matrix">The
      reference matrix</a>
    </h4>
<p>
      There reference matrix is the only thing written in BoostBook. It is an XML
      file with an overview of all Boost.Geometry functionality. Presenting it like
      this is not possible within QuickBook, therefore BoostBook XML is used here.
      It is included by the QuickBook code. The Boost.Asio documentation contains
      a similar reference matrix.
    </p>
<h4>
<a name="geometry.aboutdoc.h2"></a>
      <span class="phrase"><a name="geometry.aboutdoc.mixing_quickbook_into_c___code"></a></span><a class="link" href="aboutdoc.html#geometry.aboutdoc.mixing_quickbook_into_c___code">Mixing
      QuickBook into C++ code</a>
    </h4>
<p>
      With Doxygen it is possible to define aliases. Specificly for <span class="emphasis"><em>doxygen_xml2qbk</em></span>,
      the alias <span class="bold"><strong>\qbk{...}</strong></span> was defined. This alias
      <span class="bold"><strong>\qbk{...}</strong></span> add some XML-tags around the text
      inside the alias, such that that included part is recognizable by the converter.
    </p>
<p>
      So the C++ code might look like this:
    </p>
<pre class="programlisting">/*!
\brief Some explanation
\ingroup some_group
\details Some details
\tparam Geometry Description of the template parameter
\param geometry Description of the variable

\qbk{ [include reference/more_documentation.qbk] }
 */
</pre>
<p>
      First you see normal Doxygen comments. The last line uses the alias \qbk{...}
      to include a QuickBook file. So most of the documentation can be written in
      that QuickBook file: behaviour, complexity, examples, related pages, etc.
    </p>
<p>
      In the example above a QuickBook include statement is used. But any QuickBook
      code can be used, the QuickBook code does not have to be stored in a separate
      file. Two more samples:
    </p>
<pre class="programlisting">/*!
...
\qbk{
[heading Example]
[area_with_strategy]
[area_with_strategy_output]

[heading Available Strategies]
[link geometry.reference.strategies.strategy_area_cartesian Cartesian]
}
 */
</pre>
<p>
      In this example pieces of QuickBook are included, two headers, two examples
      (this is the QuickBook way - the examples are defined elsewhere), and a link.
    </p>
<h4>
<a name="geometry.aboutdoc.h3"></a>
      <span class="phrase"><a name="geometry.aboutdoc.quickbook_within_c___issues"></a></span><a class="link" href="aboutdoc.html#geometry.aboutdoc.quickbook_within_c___issues">QuickBook
      within C++ issues</a>
    </h4>
<p>
      There are two issues: the comma and the asterisk. If within the <span class="bold"><strong>\qbk</strong></span>
      alias a comma is used, it is recognized by Doxygen as another parameter, and
      therefore will not deliver the correct results, or result into errors. This
      is easily solvable by escaping comma's (by putting a backslash directly before
      the comma, \, ). It within the <span class="bold"><strong>\qbk</strong></span> alias
      an asterisk is used on the first line, it is interpreted by Doxygen as well.
      This asterisk can be escaped as well, and this time it is <span class="emphasis"><em>doxygen_qbk2xml</em></span>
      which handles this escape and translates it back into an asterisk.
    </p>
<h4>
<a name="geometry.aboutdoc.h4"></a>
      <span class="phrase"><a name="geometry.aboutdoc.overloads"></a></span><a class="link" href="aboutdoc.html#geometry.aboutdoc.overloads">Overloads</a>
    </h4>
<p>
      Boost.Geometry contains a lot of overloads, two functions with the same name
      and, for example, a different number of parameters. Or, as another example,
      a const and a non-const version. They can be marked specificly to the <span class="emphasis"><em>doxygen_xml2qbk</em></span>
      tool with the \qbk alias, by adding a specific description for the overload.
      So, for example, <span class="bold"><strong>\qbk{distinguish,with strategy}</strong></span>
      will result in another page where the text "with strategy" is added,
      and it is processed as "_with_strategy" within the QuickBook section
      name.
    </p>
<h4>
<a name="geometry.aboutdoc.h5"></a>
      <span class="phrase"><a name="geometry.aboutdoc.overloads_and_sharing_documentation"></a></span><a class="link" href="aboutdoc.html#geometry.aboutdoc.overloads_and_sharing_documentation">Overloads
      and sharing documentation</a>
    </h4>
<p>
      With overloads, part of the documentation must be shared, and other part must
      not. The descriptions are often the same. But the examples are usually not.
      So it is a balance between sharing documentation, including shared documentation,
      avoiding too much separate QuickBook files containing pieces of documentation
      and avoiding including too much QuickBook code within the C++ code...
    </p>
<h4>
<a name="geometry.aboutdoc.h6"></a>
      <span class="phrase"><a name="geometry.aboutdoc.doxygen_aliases"></a></span><a class="link" href="aboutdoc.html#geometry.aboutdoc.doxygen_aliases">Doxygen
      aliases</a>
    </h4>
<p>
      While documenting a large library, it is unavoidable that you have to document
      the same parameters in different places. For example, the template parameter
      <span class="bold"><strong>Geometry</strong></span>, and the variable <span class="bold"><strong>geometry</strong></span>,
      occur at least 100 times in our library.
    </p>
<p>
      To avoid repeating the same text again and again, Doxygen aliases are used.
      So \tparam_geometry means that the generic description for a template parameter
      geometry is inserted. \param_geometry does the same for a parameter. This is
      all handled by Doxygen itself. The aliases can also be parameterized, for example:
      <span class="bold"><strong>\return_calc{area}</strong></span> is expanded to: <span class="emphasis"><em>The
      calculated area</em></span>
    </p>
<p>
      This is for Doxygen alone and is not related to <span class="emphasis"><em>doxygen_xml2qbk</em></span>
      or QuickBook.
    </p>
<h4>
<a name="geometry.aboutdoc.h7"></a>
      <span class="phrase"><a name="geometry.aboutdoc.quickbook_macros"></a></span><a class="link" href="aboutdoc.html#geometry.aboutdoc.quickbook_macros">QuickBook
      macros</a>
    </h4>
<p>
      QuickBook has the same functionality for the same purpose: macro's or templates
      can be defined. Within Boost.Geometry this is used in the QuickBook parts of
      the documentation. So the general rule would be: where it is possible to use
      a Doxygen alias, we use a Doxygen alias. If we are outside the scope of Doxygen
      and we want to define a macro, we use a QuickBook macro.
    </p>
<p>
      Stated otherwise, we don't use the generated Doxygen documentation, but if
      we would, it would look correct and would not be unreadable by unexpanded QuickBook
      macro's.
    </p>
<h4>
<a name="geometry.aboutdoc.h8"></a>
      <span class="phrase"><a name="geometry.aboutdoc.code_examples"></a></span><a class="link" href="aboutdoc.html#geometry.aboutdoc.code_examples">Code
      examples</a>
    </h4>
<p>
      We favour the use of code examples within the generated documentation. Example
      code must be correct, so examples must compile, run, and produce the correct
      results. QuickBook has a nice solution to include and present C++ source code,
      including syntax highlighting. So we generally present the example (a complete
      example including necessary headerfiles) and the output. Asserts are not used
      here, these are examples and no tests.
    </p>
<p>
      So this is why we did enclose in the \qbk alias above:
    </p>
<pre class="programlisting">[heading Example]
[area_with_strategy]
[area_with_strategy_output]
</pre>
<p>
      We define a heading, we include the example (here denoted by the name "area_with_strategy")
      and we include the output of the sample "area_with_strategy_output".
      Note that we simulate that the output is C++ code, a trick giving the appropriate
      formatting (there might be other ways to get the same effect).
    </p>
<p>
      All these QuickBook examples are included in the doc/src/examples/* folders,
      where also a Jamfile is present. Running bjam there ensures that nothing is
      broken in the examples.
    </p>
<p>
      Some examples, if relevant, are accompagnied by images. The images are generated
      by the example themselves (though marked as commented out for QuickBook), deliver
      an SVG file which can be manually converted to a PNG (I'm using InkScape for
      that which is quite convenient).
    </p>
</div>
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<td align="right"><div class="copyright-footer">Copyright © 2009-2021 Barend Gehrels,
      Bruno Lalande, Mateusz Loskot, Adam Wulkiewicz, Oracle and/or its affiliates<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
      </p>
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